Interaction of glioma-associated microglia/macrophages and anti-PD1 immunotherapy

Mechanism of LINC01018/miR-182-5p/Rab27B in the immune escape through PD-L1-mediated CD8+ T cell suppression in glioma

BACKGROUND

Glioma is a malignant tumor associated with poorer prognosis. This study aims to elucidate the mechanism of LINC01018/miR-182-5p/Rab27B axis in PD-L1-mediated CD8+ T cell suppression in the progression of gliomas.

METHODS

LINC01018, miR-182-5p, and Rab27B expression levels in glioblastoma tissues were measured. The proportion of infiltrating macrophages and monocytes and CD8+ T cell function were assessed. The relationship between miR-182-5p and Rab27B was analyzed. Glioma cell activity, invasion, and migration were measured. The expression of E-cadherin, N-cadherin, Vimentin, PD-L1, iNOS, and CD206 was determined. Glioma cell-derived EVs were isolated, and the co-localization of Rab27B and PD-L1 and the binding of Rab27B to PD-L1 were analyzed. The endocytosis of EVs by microglia was assayed. The impact of LINC01018/miR-182-5p/Rab27B on glioma growth was observed. The function of macrophages and CD8+ T cells in tumors was analyzed.

RESULTS

Rab27B was downregulated, and infiltrating macrophages and monocytes were increased in glioblastoma. miR-182-5p inhibited Rab27B expression. Rab27B knockdown reverses the inhibitory effect of LINC01018 overexpression on glioma cell growth. Glioma cells-derived EVs with low Rab27B expression carried more PD-L1 to increase PD-L1 expression and M2 polarization in microglia. LINC01018 overexpression reduced macrophages in orthotopic tumors. CD8+ T cell numbers showed no significant difference, but TIM-3 increased and IFN-γ decreased. miR-182-5p inhibition enhanced the therapeutic effect of anti-PD-L1, which was reversed after glioma cell-derived EVs.

CONCLUSION

LINC01018 promotes PD-L1-mediated CD8+ T cell suppression via the miR-182-5p/Rab27B axis in glioma cell-derived EVs, thereby contributing to immune escape in gliomas.

Ruxolitinib suppresses tumor growth in PTEN-deficient glioblastoma by inhibiting the STAT3-PDL1 axis-mediated the M2 polarization of macrophages

BACKGROUND

Glioblastoma (GBM) is the most malignant form of brain tumor, and GBM patients with poorer prognosis and highly immunosuppressive tumor microenvironment (TME) often exhibit PTEN deficiency in their tumor tissues. Therefore, new therapeutic strategies targeting immunosuppressive TME maybe useful in PTEN-deficient GBM.

METHODS

Bioinformatics was used to assess gene expression, survival time and immunoinfiltration in PTEN-deficient GBM. CRISPR-Cas9 was used to construct gene knockout cell lines. C57BL/6 mouse orthotopic GBM models were used to conduct survival analysis and evaluate treatment effect of Ruxolitinib. Flow cytometry, immunohistochemistry, immunofluorescence and quantitative real-time PCR (qRT-PCR) to detect the polarization of macrophages. Immunoblotting, immunohistochemistry, qRT-PCR, enzyme linked immunosorbent assay, and dual-luciferase reporter assay were used to conduct mechanism research.

RESULTS

We identified that the elevated levels of phosphorylated STAT3 (p-STAT3) in PTEN-deficient GBM facilitate PDL1 transcription, which subsequently drives M2 polarization of macrophages. Furthermore, PTEN deficiency, along with high expression levels of STAT3 and PDL1, are associated with a shorter survival time in GBM patients. Notably, in orthotopic mouse models of GBM with PTEN deficiency, Ruxolitinib therapy reduces the levels of p-STAT3 and PDL1, inhibits the infiltration of M2 macrophages, and suppresses tumor growth.

CONCLUSIONS

The STAT3-PDL1 axis plays a crucial role in the M2 polarization of macrophages in PTEN-deficient GBM. The blockade of the STAT3-PDL1 axis by Ruxolitinib regulates the anti-tumor immune response and curtails tumor progression in PTEN-deficient GBM, highlighting its significant clinical implications.

Exploring tumor-associated macrophages in glioblastoma: from diversity to therapy

Glioblastoma is the most aggressive and lethal cancer of the central nervous system, presenting substantial treatment challenges. The current standard treatment, which includes surgical resection followed by temozolomide and radiation, offers limited success. While immunotherapies, such as immune checkpoint inhibitors, have proven effective in other cancers, they have not demonstrated significant efficacy in GBM. Emerging research highlights the pivotal role of tumor-associated macrophages (TAMs) in supporting tumor growth, fostering treatment resistance, and shaping an immunosuppressive microenvironment. Preclinical studies show promising results for therapies targeting TAMs, suggesting potential in overcoming these barriers. TAMs consist of brain-resident microglia and bone marrow-derived macrophages, both exhibiting diverse phenotypes and functions within the tumor microenvironment. This review delves into the origin, heterogeneity, and functional roles of TAMs in GBM, underscoring their dual roles in tumor promotion and suppression. It also summarizes recent progress in TAM-targeted therapies, which may, in combination with other treatments like immunotherapy, pave the way for more effective and personalized strategies against this aggressive malignancy.

In vivo self-assembled albumin nanoparticle elicit antitumor immunity of PD-1 inhibitor by imaging and clearing tumor-associated macrophages

Eliciting anti-tumor immune responses and improving the tumor microenvironment crucial for boosting the effectiveness of anti-PD-1 immunotherapy. Tumor-associated macrophages (TAMs), the primary types of immune cells infiltrating tumors, play a critical role in the formation of an immunosuppressive microenvironment. In this study, we constructed a novel Evans Blue (EB)-based in vivo self-assembled nanocarrier system, mUNO-EB-ICG-Fc@Alb nanoparticles (designated as MA NPs), for targeted imaging and clearance of M2-TAMs to elicit antitumor immunotherapy of PD-1 inhibitor. In vitro experiments demonstrated the specific fluorescence imaging and killing effect of MA NPs on M2-TAMs. In vivo experiments shown that MA NPs-induced chemodynamic therapy (CDT) successfully reversed the tumor immunosuppressive microenvironment (ITM), promoted intratumoral infiltration of T lymphocytes, and ultimately enhancing the anti-tumor immunotherapy effect of PD-1 inhibitors. This study might provide good inspiration for improving the therapeutic efficacy of cancer immunotherapy.

Exploring the impact of ITGB2 on glioma progression and treatment: Insights from non-apoptotic cell death and immunotherapy

In the realm of glioma treatment, our groundbreaking research has uncovered the pivotal role of Integrin Beta 2 (ITGB2) in non-apoptotic cell death and its profound implications for immunotherapy efficacy. Gliomas, known for their aggressive and infiltrative nature, demand innovative therapeutic strategies for improved patient outcomes. Our study bridges a critical gap by examining the interplay between non-apoptotic cell death and immunotherapy response in gliomas. Through comprehensive analysis of ten diverse glioma datasets, we developed a unique death enrichment score and identified ITGB2 as a significant risk marker. This study demonstrates that ITGB2 can predict immune activity, mutation characteristics, and drug response in glioma patients. We reveal that ITGB2 not only mediates glioma proliferation and migration but also crucially influences immunotherapy responses by modulating the interaction between gliomas and macrophages by single-cell sequencing analysis (iTalk and ICELLNET). Employing a variety of molecular and cellular methodologies, including in vitro models, our findings highlight ITGB2 as a potent marker in glioma biology, particularly impacting macrophage migration and polarization. We present compelling evidence of ITGB2's dual role in regulating tumor cell behavior and shaping the immune landscape, thereby influencing therapeutic outcomes. The study underlines the potential of ITGB2-targeted strategies in enhancing the efficacy of immunotherapy and opens new avenues for personalized treatment approaches in glioma management. In conclusion, this research marks a significant stride in understanding glioma pathology and therapy, positioning ITGB2 as a key biomarker and a promising target in the quest for effective glioma treatments.

Inhibition of the TCF12/VSIG4 axis by palbociclib diminishes the proliferation and migration of glioma cells and decreases the M2 polarization of glioma-associated microglia

The CDK4/CDK6 inhibitor palbociclib has shown the encouraging promise in the treatment of glioma. Here, we elucidated how palbociclib exerts suppressive functions in the M2 polarization of glioma-related microglia and the progression of glioma. Xenograft experiments were used to evaluate the function in vivo. The mRNA levels of transcription factor 12 (TCF12) and VSIG4 were detected by RT-qPCR, and their protein levels were assessed by immunoblotting. Cell migration was tested by wound-healing assay. Cell cycle distribution and M1/M2 microglia phenotype analysis were performed by flow cytometry. The levels of IFN-γ, TNF-α, IL-6，and TGF-β were measured by ELISA. The TCF12/VSIG4 association was verified by luciferase reporter and chromatin immunoprecipitation (ChIP) assays. In U251 and LN229 glioma cells, TCF12 and VSIG4 were overexpressed, and palbociclib reduced their expression levels. TCF12 upregulation enhanced the proliferation and migration of glioma cells and the M2 polarization of glioma-associated microglia in vitro as well as the tumorigenicity of U251 glioma cells in vivo, which could be reversed by palbociclib. Mechanistically, TCF12 could enhance VSIG4 transcription and expression by binding to the VSIG4 promoter. TCF12 deficiency led to repression in glioma cell proliferation and migration as well as microglia M2 polarization, which could be abolished by increased VSIG4 expression. Our study reveals the novel TCF12/VSIG4 axis responsible for the efficacy of palbociclib in combating glioma, offering a rationale for the application of palbociclib in glioma treatment.

From glioma gloom to immune bloom: unveiling novel immunotherapeutic paradigms-a review

In tumor therapeutics, the transition from conventional cytotoxic drugs to targeted molecular therapies, such as those targeting receptor tyrosine kinases, has been pivotal. Despite this progress, the clinical outcomes have remained modest, with glioblastoma patients' median survival stagnating at less than 15 months. This underscores the urgent need for more specialized treatment strategies. Our review delves into the progression toward immunomodulation in glioma treatment. We dissect critical discoveries in immunotherapy, such as spotlighting the instrumental role of tumor-associated macrophages, which account for approximately half of the immune cells in the glioma microenvironment, and myeloid-derived suppressor cells. The complex interplay between tumor cells and the immune microenvironment has been explored, revealing novel therapeutic targets. The uniqueness of our review is its exhaustive approach, synthesizing current research to elucidate the intricate roles of various molecules and receptors within the glioma microenvironment. This comprehensive synthesis not only maps the current landscape but also provides a blueprint for refining immunotherapy for glioma, signifying a paradigm shift toward leveraging immune mechanisms for improved patient prognosis.

Interactions between microglia and glioma in tumor microenvironment

Gliomas, the most prevalent primary tumors in the central nervous system, are marked by their immunosuppressive properties and consequent poor patient prognosis. Current evidence emphasizes the pivotal role of the tumor microenvironment in the progression of gliomas, largely attributed to tumor-associated macrophages (brain-resident microglia and bone marrow-derived macrophages) that create a tumor microenvironment conducive to the growth and invasion of tumor cells. Yet, distinguishing between these two cell subgroups remains a challenge. Thus, our review starts by analyzing the heterogeneity between these two cell subsets, then places emphasis on elucidating the complex interactions between microglia and glioma cells. Finally, we conclude with a summary of current attempts at immunotherapy that target microglia. However, given that independent research on microglia is still in its initial stages and has many shortcomings at the present time, we express our related concerns and hope that further research will be carried out to address these issues in the future.

Dynamic change in Siglec-15 expression in peritumoral macrophages confers an immunosuppressive microenvironment and poor outcome in glioma

Background

Sialic acid-binding immunoglobulin-like lectin-15 (Siglec-15) was reported to be a novel immune checkpoint molecule comparable to programmed cell death 1 ligand 1 (PD-L1). However, its expression profile and immunosuppressive mechanisms in the glioma tumor microenvironment have not yet been fully explored.

Objectives

To identify the expression profile and potential function of Siglec-15 in glioma tumor microenvironment.

Methods

We investigated Siglec-15 and PD-L1 expression in tumor tissues from 60 human glioma patients and GL261 tumor models. Next, Siglec-15 knockout macrophages and mice were used to elucidate the immunosuppressive mechanism of Siglec-15 impacting macrophage function.

Results

Our results demonstrated that high levels of Siglec-15 in tumor tissues was positively correlated with poor survival in glioma patients. Siglec-15 was predominantly expressed on peritumoral CD68⁺ tumor-associated macrophages, which accumulated to the highest level in grade II glioma and then declined as grade increased. The Siglec-15 expression pattern was mutually exclusive with that of PD-L1 in glioma tissues, and the number of Siglec-15⁺PD-L1^- samples (n = 45) was greater than the number of Siglec-15^-PD-L1⁺ samples (n = 4). The dynamic change in and tissue localization of Siglec-15 expression were confirmed in GL261 tumor models. Importantly, after Siglec15 gene knockout, macrophages exhibited enhanced capacities for phagocytosis, antigen cross-presentation and initiation of antigen-specific CD8⁺ T-lymphocyte responses.

Conclusion

Our findings suggested that Siglec-15 could be a valuable prognostic factor and potential target for glioma patients. In addition, our data first identified dynamic changes in Siglec-15 expression and distribution in human glioma tissues, indicating that the timing of Siglec-15 blockade is critical to achieve an effective combination with other immune checkpoint inhibitors in clinical practice.